This invention relates to apparatus for clearing clogged drain lines, and, more particularly, to an apparatus operable to direct a burst of pressurized air against the column of water behind an obstruction in a clogged drain line to generate a shockwave in the water and dislodge the obstruction.
Numerous devices have been proposed for the removal of obstructions from drain and plumbing lines in which an impulse of pressurized air is applied to the column of standing water behind the obstruction to generate a shockwave in the water to dislodge the obstruction. Devices of this type generally include a housing having a chamber formed with a discharge opening which is adapted to communicate with the drain line to be cleared. A valve, usually in the form of a plunger or piston, is movable within the chamber between a position where it seals the discharge opening to permit pressurization of the chamber, and an exhaust position where its seal with the discharge opening is broken to release the pressurized air from the chamber and into the clogged drain line. Devices of this general type are shown, for example, in U.S. Pat. Nos. 3,426,774; 3,789,861; 3,879,771 and 4,097,937.
One of the disadvantages of the drain cleaning devices disclosed in the patents mentioned above is that the means provided to effect the release of pressurized air from the chamber is inefficient and often difficult to operate. For example, in U.S. Pat. No. 3,426,774 to Conn, the discharge opening of the chamber is opened and closed by a valve mounted at the end of a plunger which is retractable by depressing a trigger mechanically connected to the plunger by a rack and pinion. The valve is normally biased by a spring in a closed position against the discharge opening to permit pressurization of the chamber in preparation for the release of an impulse of air. In order to release fluid from the chamber, the plunger is retracted by depressing the trigger to unseat the valve and open the discharge opening. Retraction of the plunger to an open position requires a relatively large force to be applied on the trigger because the force exerted against the valve by the pressurized fluid and the spring both act in the opposite direction urging the valve against the discharge opening.
Devices of the type described above, which provide a release or trigger mechanism mechanically connected to the piston or plunger to be retracted, are difficult to operate and inefficient. The relatively large force required to depress the trigger mechanism in order to retract the plunger makes it difficult to depress the trigger quickly. If the valve which seals the discharge opening in the chamber is retracted slowly, the pressurized air begins to leak out of the chamber before the trigger is completely depressed, resulting in a gradual pressure drop in the chamber rather than an immediate pressure drop. In order for devices of this type to achieve maximum efficiency, it is necessary to release a high pressure impulse or burst of air against the water column behind the obstruction to obtain effective shockwaves in the water to unclog the drain line. A gradual release of pressurized air from the chamber due to a slowly retracted piston or valve produces a lower pressure, less effective impulse of air.
Another problem with drain cleaning devices of the type described above is that the cross section of the discharge opening in the chambers is often relatively small compared to the diameter of the drain line to be unclogged. This reduces the overall force of the air impulse applied to the standing column of water behind the obstruction and limits the effectiveness of the shockwaves intended to remove the obstruction.
Many drain cleaning devices of the type described above are relatively expensive to manufacture because they are fabricated with several parts which require machining. In addition, many prior art devices are relatively long and bulky which presents a problem in their use for some applications where the openings to the drain line are in a restricted space, such as the drain in a sink having a faucet mounted in a fixed position above the drain.